In the oil and gas industry, geophysical prospecting is commonly used to aid in the search for and evaluation of subterranean formations. Geophysical prospecting techniques yield knowledge of the subsurface structure of the earth, which is useful for finding and extracting valuable mineral resources, particularly hydrocarbon deposits such as oil and natural gas.
One technique of geophysical prospecting is a seismic survey. In a seismic survey, an acoustic wave, referred to as a seismic signal, is generated by one or more seismic energy sources. Terrestrial seismic energy sources may include, for example, shots of buried dynamite or seismic air guns. Marine seismic energy sources may include, for example, air guns, water guns, or marine vibrators.
The seismic signal propagates into the geological strata of the earth and reflects off sub-surface features, referred to as seismic reflectors, which present varying acoustic impedances. Such seismic reflectors are typically interfaces between subterranean formations having different elastic properties which lead to differences in acoustic impedance at the interfaces.
The reflected waves may be received by multiple seismic sensors, referred to as receivers. Land seismic sensors may include, for example, geophones, while marine seismic sensors may include, for example, geophones and hydrophones. Each sensor is configured to convert the wave information to electrical signals, referred to as seismic data. In a typical configuration, the sensors may be configured in a two-dimensional (2D) array such that three-dimensional (3D) seismic data (seismic volumes) may be obtained. The seismic data may be recorded and subsequently processed to yield information relating to the geologic structure and properties of the subterranean formations and their potential hydrocarbon content.
One challenge in processing the seismic data to obtain useful information about the geological structure is due to the presence of noise in the seismic data. The noise generally includes both incoherent and coherent noise (often in the form of multiples). The attenuation of incoherent and coherent noise in seismic data is one of the most labor-intensive and challenging aspects of seismic data processing.
Note that the figures provided herewith are not necessarily to scale. They are provided for purposes of illustration to ease in the understanding of the presently-disclosed invention.